Motor and aviation fuels



Patented July 4, 1950 asnsee UNITED STATES PATENT OFFICE Sunbury-on-Thames,

England,

assignors to Anglo-Iranian Oil Company Limited, London, England, a British joint-stock corporation.

No Drawing.

Claims. 1

invention relates to the stabilisation of motor and aviation fuels containing anti-knock reagents.

The use of anti-knock reagents containing tetra-ethyl lead is widely known in the preparation of high quality liquid fuels for use in internal combustion engines. In recent years there has been a growing demand for liquid fuels showing still greater resistance to knock and particularly for aviation fuels. To facilitate the production of these high quality fuels offlcial specifications have appreciably relaxed the lead tolerance, and

Application July 15, 1946, Serial In Great Britain July 14, 1945 much larger proportions of anti-knock reagents are now permitted in such fuels.

It is known that gasoline containing tetra-ethyl lead, and particularly aviation gasolines which normally contain a higher proportion of the antiknock reagent than motor gasolines, tend to become unstable on storage, and to deposit a white precipitate containing lead. This instability tends to become more marked as the lead content of the fuel rises and thus the relaxation in lead tolerance allowed by official specifications has accentuated the instability of these leaded liquid fuels.

We have found that elemental sulphur, hydrogen sulphide, carbon disulphide, thiophene and dialkyl disulphides have a marked effect in producing instability, and some evidence that instability is also promoted by certain olefines.

Alkyl sulphides, (thioethers) and mercaptans do not however appear to have any appreciable effect on the stability of a leaded fuel.

According to the invention, liquid fuels conta ining tetra-ethyl lead are stabilised by the addition thereto of a minor proportion of a lead salt.

Both organic and inorganic lead salts and mixtures of organic and inorganic lead salts may be used.

We have found that the proportion of stabilising agent to be added need not exceed 0.01% and in many cases satisfactory results are achieved when the fuel contains as little as 0.001% of the stabilising agent. A total proportion not in excess of 0.02% of one, or more than one, lead salt may be incorporated in the fuel.

The lead salt or lead salts may be incorporated by solution in the fuel in a. number of ways. They may, for example, be added to the finished fuel, or to any of the constituents of the fuel prior to blending, or to the anti-knock reagent, or they may be incorporated during the blending process, or during the leading operation, or incorporated in the finished fuel by passing the fuel through a vessel containing the lead salt or an aqueous solution thereof.

.Lead salts are generally only slightly soluble in motor and aviation fuels and in order successfully to incorporate a lead salt in the fuel it may in certain cases be necessary to add an excess of the salt to the fuel and to decant the exceedingly dilute solution formed. It is also advantageous to add the lead salt, particularly lead acetate, in the form of an alcoholic solution, since an apparent increase in the solubility of the salt in the fuel is thereby attained.

The following examples show that of the lead salts tested, the acetate gives the most consistently good results, that all the salts tested had some stabilising effect, and that salts such as lead chromate, lead nitrate and lead chloride appear to be selective in effect, showing excellent stabilising properties where the sulphur is present in organically combined form, as in thiophene, but showing no beneficial effect when the sulphur is present in inorganically combined form, as in carbon disulphide.

In each of the following examples the fuel contained 5.5 MI. T. E. L./I. G. and the storage tests, unless otherwise stated, were carried out in the dark at a temperature of 120 F. The measure of instability under the conditions of test was the time taken in days for the appearance of- (a) a barely visible trace of precipitate (b) a clearly visible medium precipitate (c) aheavy precipitate.

The time taken to form a medium or heavy precipitate is thus a measure of the stability to be expected in practice. The formation of a mere visible trace of precipitate is unimportant.

Example I.The fuel used in this example was a sulphur free isooctane, to which thiophene had been added in quantity sufiicient to give the fuel a sulphur content of 0.005% by weight.

The following determinations were made:

No. of days for deposition oi precipitate Inhibitor Trace Medium Heavy None l 2 Fuel saturated with lead acetate at F. 104 Fuel saturated with lead acetate 22 25 28 Fuel saturated with lead chromate 9 32 Fuel saturated with lead nitrate" 1 32 Fuel saturated with lead chloride- 6 l0 l5 Fuel+.00l% Pb as lead stearate 1 i7 36 Fuel+.00l% Pb as lead palmitate l 8 Fuel+.00l% Pb as lead oleate 1 4 5 Fuel after washing with vol..of 10% lead acetate solution 32 64 76 Example II .The fuel used in this example was a sulphur free isooctane to which carbon disulphide had been added in quantity suilicient to give the fuel a sulphur content of 0.005% by weight.

The following determinations were made:

No. oi days (or deposition Fuel+.00l7 Pb as lead stear 10 Fuel-+0019 Pb as lead palmitate 9 Fuel+.00l a Pb as lead oleate 16 Fuel after washing with 100% vol. oi 10% lead acetate solution Ezvample III .--The fuel used in this example was 100 octane aviation spirit, prepared on an industrial scale and having a sulphur content of 0.022% by weight, the sulphur compounds present being unidentified.

The fuel deposited a medium precipitate after one day storage, and a heavy precipitate after two days. v

A comparable sample was saturated with lead chloride at 60 F. and'stored in the dark at 120 F., a heavy precipitate being deposited after six days.

Example I V.-The fuel used in this example was a 100 octane aviation spirit, prepared on an industrial scale, and having a sulphur content of 0.014 by weight, the sulphur compounds present being unidentified.

The fuel deposited a light precipitate after one day, and a heavy precipitate after three days.

A comparable sample was washed with 100% by volume of a 10% lead acetate solution, and deposited a light precipitate in two days, a medium precipitate in five days, and a heavy precipitate in six days.

The following example shows the efi'ect of mixtures of lead salts in equal proportions by weight.

Example V.The fuel used in this example was a. sulphur-free isooctane to which thiophene had been added in quantity sufficient to give the fuel a sulphur content of 0.005% by weight.

The following determinations were made:

No. of days for deposition of precipitate Inhibitor Trace Medium Heavy Nrmn 1 2 Fuel saturated with lead chloride/lead acetate l 13 21 Fuel saturated with lead chloride/lead nitrate 11 Fuel saturated with lead palmitate/lead aceta 6 7 We claim:

1. A stabilized gasoline for use in internal combustion engines, said gasoline containing tetra ethyl lead as anti-knock reagent and a lead salt of a fatty acid as stabilizing agent.

2. A stabilized gasoline for use in internal combustion engines, said gasoline containing tetra ethyl lead as anti-knock reagent and an amount not exceedin 0.02% by weight of a lead salt of a fatty acid as stabilizing agent.

3. A stabilized gasoline as in claim 1 in which the lead salt is lead acetate.

4. A stabilized gasoline as in claim 2 in which the lead salt is lead acetate.

' 5. A stabilized gasoline for use in internal combustion engines, said gasoline containing sulphur in organically combined form and, as added constituents, tetra ethyl lead as anti-knock reagent and a mixture of a lead salt of a fatty acid and an inorganic lead salt as stabilizing agent.

6. A stabilized gasoline as in claim 5 in which said mixture is present in an amount not exceeding 0.02% by weight.

7. A stabilized gasoline as in claim 6 in which the lead salts of the mixture are present in substantially equal proportions by weight.

8. A stabilized gasoline for use in internal combustion engines, said gasoline containing tetraethyl lead as an anti-knock reagent, a lead salt of a fatty acid as a stabilizing agent and an amount of alcohol to increase the solubility of the organic lead salt in the gasoline.

9. A stabilized gasoline as in claim 8 in which the organic lead salt is present in an amount not exceeding 0.02 by weight.

10. A stabilized gasoline as in claim 8 in which the organic lead salt is lead acetate.

11. A stabilized gasoline as in claim 9 in which the organic lead salt is lead acetate.

12. A stabilized gasoline for use in internal combustion engines, said gasoline containing tetraethyl lead as an anti-knock reagent, and being saturated with a mixture of lead salts of fatty acids as a stabilizing agent.

13. A stabilized gasoline as in claim 12 in which said mixture is present in an amount not exceeding 0.02% by weight.

14. A stabilized gasoline as in claim 12 in which lead acetate and lead palmitate are the organic lead salts.

15. A stabilized gasoline as in claim 13 in which lead acetate and lead palmitate are the organic lead salts of the mixture.

16. A stabilized gasoline for use in internal combustion engines, said gasoline containing tetraethyl lead as an anti-knock reagent, and being saturated with a mixture of lead acetate and lead chloride as a stabilizing agent.

17. A stabilized gasoline as in claim 16 in which said mixture is present in an amount not exceeding 0.02% by weight.

18. A stabilized gasoline for use in internal combustion engines, said gasoline containing tetra-ethyl lead as anti-knock reagent and lead stearate as stabilizing agent.

19. A stabilized gasoline as in claim 18 in which said lead stearate is present in an amount not exceeding 0.02% by weight.

20. A stabilized gasoline for use in internal combustion engines, said gasoline containing tetra-ethyl lead as anti-knock reagent and lead palmitate as stabilizing agent.

21. A stabilized gasoline as in claim 20 in which said lead palmitate is present in an amount not exceeding 0.02% by weight.

22. A, stabilized gasoline for use in internal combustion engines, said gasoline containing tetra-ethyl lead as anti-knock reagent and lead oleate as stabilizing agent.

23. A stabilized gasoline as in claim 22 in which said lead oleate is present in an amount not exceeding 0.02% by weight. 7

24. A stabilizing gasoline for use in internal combustion engines, said gasoline containing tetra-ethyl lead as anti-knock reagent, and a lead salt of a fatty acid selected from the class consisting of lead acetate, lead stearate, lead palmitate and lead oleate, as stabilizing agent.

36. A stabilizing monne as in chum 24 in which said lead salt is present in an amount not "REFERENCES CITED The following references are or record in file of this patent:

UNITED sums PA'I'ENTS Number Name Date 3 811!!! by Weight- 1 0 03 m m 11 937 W ARTHUR PARTRIDGE- 2,310,739 Cook Apr. 13, 1943 HAROLD JOHN ALTY- b 2,433,: De Vertex- Dec. 23, 194': 

1. A STABILIZED GASOLINE FOR USE IN INTERNAL COMBUSTION ENGINES, SAID GASOLINE CONTAINING TETRA ETHYL LEAD AS ANTI-KNOCK REAGENT AND A LEAD SALT OF A FATTY ACID AS STABLIZING AGENT. 